About the middle of July, the outside air temp, normally displayed on the radio LCD screen of my 2014 Chevy Sonic, disappeared. No biggie, I didn't need it to tell me it was fooking hot! Then, on August 8, the AC suddenly quit working, and it was still fooking hot.
Opening the hood, I found little tiny footprints on the engine, as well as rodent turds near the fuse box. I didn't see any evidence of chewed wires, and couldn't find any obvious problems, and 2 different scanners didn't show anything. The system had a full charge of refrigerant.
I read on the 'net that the Ambient Temperature Sensor, mounted in the grill, would prevent the AC from working, but the AC had worked for several weeks after the sensor had failed??
The part was only $14, but, according to the 'net, you have to pull the whole front bumper off the car to replace it. I did find a youtube video where a guy pried out an insert in the bumper to access it, but it didn't want to come out. I then removed the front half of the inner fender liner, and found a pair of wires, that appeared to head off towards the sensor, with one of them chewed completely apart. Wow, looks like an easy fix!!! I twisted the two ends of the wire back together, and started the car. After a few seconds, the temp appeared on the display:-39F. WTF? Of course, if the computer thinks it's that cold, it won't allow the AC to come on. I thought maybe I didn't get a good connection, so I used a jumper with alligator clips, but got the same -39F. I decided there must still be a problem with the sensor, so I used brute force to pry back the insert in the bumper, sending bit's of plastic flying when it came free, and then was able to reach in with my left arm up to the elbow (with thoughts that I might get stuck and didn't have my phone) to pull the sensor out. I plugged in the new sensor, started the car, and the display said -39F. WTF!!! I was going to try shorting out the two wires, but there wasn't a convenient way to do it with the plug, so I tried without a sensor plugged in at all. The temp disappeared from the display, but now the AC worked!!??? I plugged a sensor in, and back to -39F and no AC.
By that time, it was getting dark, I was bruised, bleeding, and sore from working on my knees and all the getting down and back up, and thoroughly confused. As I was gathering my tools, I had a thought to try disconnecting the battery; I had tried that already, but that was before finding the broken wire. After a couple of minutes, I reconnected the battery, and with a sensor plugged in, started the engine. After a few seconds, 78F pops up on the display!
Somehow, the computer got invalid data locked in or something? Disconnecting the battery on this car doesn't even erase the programmed radio stations! I never had to do all the extra work to remove the sensor, and there was no way to reinstall the sensor in the grill with the limited access, so I drilled an existing hole behind the bumper insert larger and plugged the sensor in there. That part pissed me off.